Liquid spray apparatus are widely used in a variety of applications. The simplest form of a liquid spray apparatus involves a manual pump mechanically connected to a piston that operates to draw liquid from a container, and also to discharge liquid from a collection chamber. For many apparatus, a manual pump trigger is actuated by the user to move a piston in a collection chamber against a spring force to discharge liquid from the collection chamber out through an orifice. Upon release of force against the actuator, the spring force acts to push the piston back toward an initial position, wherein a reduced pressure is developed in the collection chamber as a motive force to drive liquid from the container into the collection chamber. Typically, one-way valves at the inlet and the outlet of the collection chamber control the collection and discharge of the liquid. In this common arrangement, liquid is dispensed from the sprayer only as the actuator is manipulated to move the piston through the collection chamber during the “discharge” portion of the cycle. In other words, liquid is not dispensed from the sprayer apparatus during the “collection” portion of the pumping cycle.
Another common type of liquid spray apparatus is a pressure sprayer, in which a pressure, typically pneumatic, is developed in a chamber through either manual or automatic means. Release from the pressure chamber is controlled by a valve that may be selectively operated by the user to introduce an elevated pressure into a liquid chamber, thereby driving liquid out from the liquid chamber through an orifice. Liquid emission will continue for so long as sufficient driving pressure is available in the pressure chamber. While pressure sprayers are useful for continuous spray applications, the mechanisms involved are typically more expensive to produce than the manual individual pump cycle spray apparatus described above, since pressure sprayers require a pressure chamber separate from the liquid chamber, and/or additional valving to accommodate the pressurization mechanism.
A need therefore exists for a liquid spray apparatus that is capable of continuous or semi-continuous emission in a compact and inexpensive manual pump spray mechanism. With such an apparatus, the user is able to maintain liquid emission for a period of time between pumping actions.